This invention relates to an internal combustion engine having a single intake valve for each cylinder, which is fed fresh intake charge by primary and secondary intake port passages. Flow through the secondary passage is selectively controlled according to an engine control algorithm.
An internal combustion engine having a single intake valve and dual intake manifold runners is disclosed in U.S. Pat. No. 4,930,468 which is assigned to the Assignee of the present invention. In an engine according to the present invention, a single intake poppet valve is located so as to control the flow of charge into the cylinder. An intake port, which conducts fresh charge to the intake valve, has a vertical dividing wall separating the port into primary and secondary passages, with the primary passage being oriented so as to cause rotational flow in the cylinder about the outermost portion of the cylinder. The secondary passage is oriented so as to cause flow directed about a radially inward portion of the cylinder. A secondary throttle valve located within the secondary passage selectively controls the flow therethrough, according to an engine control strategy. Air enters the engine via one or more intake plenums having at least one throttled charge air inlet and a plurality of primary and secondary outlets. Each engine cylinder is fed from the intake plenum via two runners. A first, or low-speed, intake runner extends from one of the primary outlets in the intake plenum to the primary port passage of each cylinder and a high-speed intake runner extends from one of the secondary outlets of the intake plenum to a secondary port passage of each cylinder. The relative lengths of the runners are selected so as to achieve desirable high-speed and low-speed tuning. The present dual induction system provides the opportunity to separate the primary and secondary passages in the intake port, as well as their respective runners, for the entire distance extending between the intake valve and the plenum. The length and cross-sectional flow areas of the runners may be optimized according to Helmholtz resonator theory or by other computer based wave dynamics calculations, or by empirical testing, to provide a ram tuning effect to increase the full load output of the engine at both low and high engine speeds.